This release drops official support for the HP
PA-RISC ('hppa'), Alpha ('alpha') and ARM ('arm') architectures.

The following are the officially supported architectures for Debian GNU/Linux
squeeze:

32-bit PC ('i386')

SPARC ('sparc')

PowerPC ('powerpc')

MIPS ('mips' (big-endian) and 'mipsel' (little-endian))

Intel Itanium ('ia64')

S/390 ('s390')

64-bit PC ('amd64')

ARM EABI ('armel')

In addition to the officially supported architectures, Debian GNU/Linux squeeze
introduces the GNU/kFreeBSD ports ('kfreebsd-amd64' and 'kfreebsd-i386') as a
technology preview. These ports are the first ones included in a Debian
release which aren't based on the Linux kernel, but instead use the FreeBSD
kernel with a GNU userland. Users of these versions however should be warned
that the quality of these ports is still catching up with the outstanding high
quality of our Linux ports, and that some advanced desktop features are not
supported yet. However, the support of common server software is strong and
extends the features of Linux-based Debian versions by the unique features
known from the BSD world. This is the first time a Linux distribution has been
extended to also allow use of a non-Linux kernel.

You can read more about port status, and port-specific information for your
architecture at the Debian port
web pages.

2.1. What's new in the distribution?

This new release of Debian again comes with a lot more software than
its predecessor lenny; the distribution includes over
10352 new packages, for a total of over 29050
packages. Most of the software in the distribution has been updated:
over 15436 software packages (this is
67% of all packages in lenny).
Also, a significant number of packages (over 4238,
18% of the packages in lenny) have
for various reasons been removed from the distribution. You will not
see any updates for these packages and they will be marked as
'obsolete' in package management front-ends.

With this release, Debian GNU/Linux updates from X.Org 7.3 to X.Org 7.5.

Debian GNU/Linux again ships with several desktop applications and
environments. Among others it now includes the desktop environments
GNOME
2.30[1], KDE
4.4.5, Xfce 4.6.2, and
LXDE 0.5.0.
Productivity applications have also been upgraded, including the
office suites
OpenOffice.org
3.2.1 and KOffice
2.2.1 as well as
GNUcash 2.2.9,
GNUmeric 1.10.8 and
Abiword 2.8.2.

Updates of other desktop applications include the upgrade to
Evolution 2.30.3
and Pidgin 2.7.3.
The Mozilla suite has
also been updated:
iceweasel
(version 3.5.13) is the unbranded
Firefox
web browser and
icedove
(version 3.0.7) is the unbranded
Thunderbird
mail client.

Among many others, this release also includes the following software updates:

Package

Version in 5.0 (lenny)

Version in 6.0 (squeeze)

Apache

2.2.9

2.2.16

BINDDNS Server

9.6.0

9.7.1

Cherokee web server

0.7.2

1.0.8

CourierMTA

0.60.0

0.63.0

Dia

0.96.1

0.97.1

Ekiga VoIP Client

2.0.12

3.2.7

Exim default email server

4.69

4.72

GNU Compiler Collection as default compiler

4.3.2

4.4.5

GIMP

2.4.7

2.6.10

the GNU C library

2.7

2.11.2

lighttpd

1.4.19

1.4.28

maradns

1.3.07.09

1.4.03

MySQL

5.0.51a

5.1.49

OpenLDAP

2.4.11

2.4.23

OpenSSH

5.1p1

5.5p1

PHP

5.2.6

5.3.2

PostfixMTA

2.5.5

2.7.1

PostgreSQL

8.3.5

8.4.5

Python

2.5.2

2.6.6

Samba

3.2.5

3.5.5

Tomcat

5.5.26

6.0.28

Debian still supports Linux Standard Base (LSB) version 3.2.

2.1.1. CDs, DVDs and BDs

The official Debian GNU/Linux distribution now ships on 7 to 8 binary
DVDs
or 44 to 53 binary CDs
(depending on the
architecture) and 6 source DVDs or 33 source
CDs. Additionally, there is a
multi-archDVD, with a subset
of the release for the amd64 and
i386 architectures, along with the source
code. Debian GNU/Linux is also released as Blu-ray
(BD) images, 2 each for the
amd64 and i386 architectures, or
one for the source code. For size reasons, some very large packages
are omitted from the CD builds; these packages fit
better in the DVD and BD builds,
so are still included there.

A new feature with squeeze is the addition of
isohybrid support to the
i386 and amd64CDs, DVDs and
BDs. To make a USB stick bootable with one of these
images used to mean following some extra procedures after downloading
the image; instead, now all that is required is to simply write the
image directly to the USB stick. For more information please see the
“Preparing Files for USB Memory Stick Booting” section in
the Installation Guide.

2.1.2. Firmware moved to the non-free section

Some drivers included in the Linux kernel used to contain non-free firmware
blobs. Starting from squeeze this firmware has been moved to separate
packages in the non-free section of the archive, such as firmware-linux. If such packages are installed,
the firmware will be loaded automatically when required.

2.1.3. Package management

The preferred program for interactive package management from a terminal is
aptitude. For a non-interactive command line interface
for package management, it is recommended to use apt-get.
apt-get is also the preferred tool for upgrades
between major releases.
If you are still using dselect, you should switch to
aptitude as the official front-end
for package management.

For squeeze APT automatically installs recommended packages by default[2].
This can be changed by adding the following line in
/etc/apt/apt.conf:

APT::Install-Recommends "false";

2.1.4. Dependency booting

An important improvement in the Debian GNU/Linux boot system is the introduction
of dependency-based boot sequencing and parallel boot. This feature is enabled
by default in new installs and it will be enabled for upgrades from
lenny, if possible.

This feature is enabled through the use of insserv
by sysv-rc to order init.d scripts based on their declared
dependencies[3].
It has been possible after a sustained effort to adapt all the boot scripts
of packages provided in the distribution as well as the boot system itself.

With dependency-based boot sequencing it is also now possible to run the boot
system scripts in parallel which can, under most circumstances, improve the
speed of the boot process. This feature is enabled by default, in new
systems and upgrades, whenever possible.
To disable it specify

CONCURRENCY=none

in /etc/default/rcS.
For more information on this feature refer to the information available in
/usr/share/doc/insserv/README.Debian.

2.1.5. Unified keyboard settings

In this new release, the settings for the keyboard have been unified so that
both the console and the Xorg server use the same settings. The keyboard
settings are now defined in the /etc/default/keyboard
configuration file which overrides the keyboard defined in Xorg's
configuration file.

The console-setup package now
handles the keyboard for both environments as well as the font
configuration for the console. You can reconfigure the keyboard layout and
related settings by executing
dpkg-reconfigure keyboard-configuration
or by manually editing the /etc/default/keyboard
configuration file.

2.1.6. Kernel mode setting

Graphics mode setting code for the most common desktop chipsets (from
Intel, ATI/AMD and NVIDIA) has moved from the respective Xorg drivers to
the Linux kernel. This provides a number of advantages, such as:

2.1.7. LDAP support

This Debian release comes with several options for implementing
client-side authentication using LDAP.
Users of the libnss-ldap and
libpam-ldap packages should
consider upgrading to
libnss-ldapd and
libpam-ldapd.

These newer packages delegate the LDAP queries to a central unprivileged
daemon (nslcd) that provides separation between the process using the LDAP
information and the daemon performing LDAP queries. This simplifies
handling of secured LDAP connections,
LDAP authentication credentials, provides a simpler
mechanism to perform connection fail-over and debugging and avoids
loading LDAP and related libraries into most
applications.

Upgrading to libnss-ldapd and
libpam-ldapd should be easy
as existing configuration information will be mostly reused.
Only for advanced configuration should any manual reconfiguration be
necessary.

These packages however currently lack support for nested groups and only
support password change using the LDAP password modify
EXOP operation.

2.1.8. The stable-updates section

Some packages from proposed-updates may also be made
available via the squeeze-updates mechanism.
This path will be used for updates which many users may wish to install
on their systems before the next point release is made, such as updates
to virus scanners and timezone data. All packages from
squeeze-updates will be included in point
releases.

The next time you run apt-get update, the
system will become aware of the packages in the
squeeze-updates section and will consider them
when looking for packages to upgrade.

Note that if APT::Default-Release is set in your
/etc/apt/apt.conf (or in any of
/etc/apt/apt.conf.d/*), then, in order for automatic
upgrades to work, it is necessary to add the following configuration block
into /etc/apt/preferences (see
apt_preferences(5) for more information):

2.1.9. backports.org/backports.debian.org

2.2. Debian Live

With squeeze Debian provides official Live systems for the amd64
and i386 architectures.

A Debian Live system is a Debian system that can be booted directly
from removable media (CD-ROMs, DVDs, USB keys) or from another computer
over the network without the need of installation. The images are
produced by a tool named live-build, which can easily be used to
create custom live images. More information about the Debian Live project
can be found at http://live.debian.net/.

2.3. Comprehensive support for neuroimaging research

Debian GNU/Linux 6.0 is the first GNU/Linux distribution release ever to offer
comprehensive support for magnetic resonance imaging (MRI) based neuroimaging
research. It comes with up-to-date software for structural image analysis
(e.g. ants), diffusion imaging and
tractography (e.g. mrtrix), stimulus
delivery (e.g. psychopy), MRI
sequence development (e.g. odin), as
well as a number of versatile data processing and analysis suites (e.g.
nipype). Moreover, this release has
built-in support for all major neuroimaging data formats. See the Debian
Science and Debian Med
task pages for a comprehensive list of included software and the NeuroDebian webpage for further
information.

[2] This change implies that disk requirements for tasks selected through the debian installer have increased too. For more information please
see the “Disk Space Needed for Tasks” chapter in the
Installation Guide.

[3] These dependences are declared through the use of
the header format specified in the Linux Standard Base (LSB)